High capacity AA batteries in the Cyton Board and associated risks
Scipio
Nigeria
@wjcroft Hi! The following link opens to show the most powerful power pack under the original link you suggested:-
https://www.adafruit.com/product/353
I trust that the 3.7 volt output of this power pack lies within the range of voltages suited to the OpenBCI Cyton Board which would appear capable of accepting a higher limit of 6 volts from 4 (1.5 volt) ‘AA’ batteries.
Although I have been using 9 volt rechargeable lithium ion batteries with a Mind Machine, there is a cautionary footnote appended to use of the adafruit batteries above which is somewhat unsettling if it is to be used with a Cyton Board in the vicinity of a patient whose EEG is being streamed and recorded. I suppose you would agree that this is simply one of those unavoidable occupational hazards that all those involved in the field have to accept.
The adafruit cautionary note runs thus:-
‘As with all Lithium ion polymer batteries and with any power source - they should be used by experts who are comfortable working with power supplies.’
I would like to know from you the rate of accidents encountered as a result of using the Cyton Board with battery power packs. My knowledge of power supplies is really rather basic and it would appear wise to have an attendant with greater technical knowledge of batteries beside me as I set up the Cyton Board, dongle and USB cable running to my computer considering the risk any patient may be exposed to regarding the Cyton Board and a connected power pack.
On a different but not unrelated issue, we do not seem to have attained a level of technology whereby rechargeable AA batteries like the one under discussion can safely provide DC output while being charged, rather like a car battery which is in use while being charged by the alternator.
Additionally, how do the batteries in the link below measure up to the adafruit ones you recommended above, especially when you consider that the former have a combined capacity of 2800mWh x four = 11200mWh?
Do you have any useful comments or words of advice?
Comments
Scipio, hi.
Here is a related recent post,
http://openbci.com/forum/index.php?p=/discussion/2255/powering-cyton-board-using-dedicated-power-supply
The Amazon link you provide, I would be cautious. The company is confusing mAh, milliamp-hours, with mWh milliwatt-hours. The fact that they would do this repeatedly, is a technical red flag. Battery capacity is measured in mAh. As a reality check, the Cyton itself is about 50ma drain. 6600 mAh / 50 mA = about 132 hours / 24 = 5.5 days of power. Adding the Daisy will use more mA, but not twice.
All lithium cells carry a precautionary label. As long as the manufacturer and charger are reputable you are fine. Adafruit is reputable. The most risk with lithium is during charging. Or if the charged battery is physically punctured or crushed. Common sense precaution will result in safe usage. I've heard the figure that two billion lithium ion cells are produced each year.
The name-you-never-heard Amazon listing, has many red flags. See the reviews as well.
Lithium single cells generate about 3.7V when full. Not sure how they produce 1.5V cells, but if some type of regulator / converter is involved, can induce noise or lost power.
Related links I came across,
https://www.indiegogo.com/projects/revolutionary-rechargeable-lithium-battery#/
https://www.amazon.com/TENAVOLTS-Rechargeable-Batteries-rechargeable-electrical/dp/B07HQ7QV7W/
https://www.candlepowerforums.com/vb/showthread.php?461572-Test-review-of-TenaVolts-AA-2775mW-(Black-blue)
States they are using a buck regulator, not a linear regulator, hence could induce some slight noise on the DC output,
http://budgetlightforum.com/node/68974
http://budgetlightforum.com/node/69034
Any type of cells placed in series, the voltage adds, but the mAh remains the same as a single battery.
Another review, referencing the teardown below,
https://www.reddit.com/r/AAMasterRace/comments/chzxhv/review_teardown_tenavolts_aa_size_15v_liion/
The use of mWh vs mAh may just be a marketing trick to make the numbers higher:
mAh * voltage = mWh
Since the voltage is 1.5, (for this type cell) those companies listing their 'capacity' numbers in mWh look 1.5 times higher than those listing capacity in the traditional mAh. The mAh ratings work well for most battery types, since voltage output of the battery changes over the discharge cycle. Since the Tenavolt offers a constant 1.5V output until cell is dead, I guess they figure it justifies using the mWh trickery.
If you try these, recommend going with the Tenavolt brand, as the other brands could be knock-off copies, and less robust. Here is a teardown of the Tenavolt showing quality level.
@wjcroft Thanks for your original reply and updates. I had in fact come across the difference in current/wattage nomenclature in the following excerpt from a highly relevant review (https://reactual.com/portable-electronics/batteries-portable-electronics/best-lithium-ion-aa-batteries.html):-
'This equation explains the difference between mWh and mAh:
miliWatt x Hour = Volts x miliAmpere x Hour or mWh = V x mAh. For more on the conversion process, read here.'
Although this is a 2016 review (https://reactual.com/portable-electronics/batteries-portable-electronics/best-lithium-ion-aa-batteries.html), what do you think about the following assertion in it and how do you rate these batteries against the "Adafruit" and "Tena" AA batteries you recommended, though I suspect that battery technology advances quite rapidly:-
'Kentli makes the best rechargeable lithium-ion AA batteries currently available. They are rated at 2800mWh, and are the only 1.5 V li-on AA batteries, making them the best choice for consumer-grade electronics.
'EXCELLENT makes 3.7V li-on batteries compatible with high drain devices like LED flashlights.'
Here are more interesting excerpts from the review above:-
'Kenli’s 1.5V offering is an ideal choice for everyday household needs. The batteries have the same voltage as a brand-new alkaline battery and won’t overpower devices that just need a stock battery.
'2800mWh is a respectable capacity, equivalent to around 1866mAh. By comparison, the Eneloop Pro has a capacity of 2550mAh. Like most NiMH batteries, the eneloop pro is 1.2V.
'Other Options
Higher voltage lithium-ion rechargeable batteries are made for high-performance flashlights and cameras, but they are not intended for use with many products. They are higher energy density and rated at 3.7V.
'EXCELLENT is one company producing higher energy density lithium ion batteries. Their 18650 batteries have a 2600mAh capacity and high quality cells. They are 3.7V and great for UV or high powered LED flashlights that consume a lot of energy.
'One word of warning to consumers: there is currently no standard size for these lithium-ion cells. Make sure to read the dimensions of each battery on Amazon before you buy to guarantee that they will fit in your device.'
By the way, regarding the above excerpt, EXCELLENT's 18650 batteries are said to be slightly bigger than normal "AA" batteries.
I still recommend the plain LiPo cells from Adafruit. Simple, and you can use with the charger they sell.
All of the AA cells that output 1.5 volts are using an internal buck regulator to step down the 3.7+ volts from the LiPo, to the 1.5 value. See previous links. These types of regulators have been known to create small amounts of power supply noise in the past. With EEG dealing in microvolts, an absolutely clean DC power source is best.
Thanks again. I am much obliged.
Oddly, the manufacturers of these newer 1.5V AA lithium cells claim their new battery design is "environmentally friendly". I don't believe that is true. Battery recycling companies (for lithium, NiMH, alkaline, NiCd, etc.) cells, are setup to tear down these cells and break up into components / chemicals. That recycling / separating equipment is already designed and in use for years.
The 1.5V AA lithium cells now contain a built in circuit board inside the top of the sealed metal case. This circuit board contains substantial amount of lead and other metals and would likely complicate recycling efforts; they would require special purpose recycling equipment to process the additional complexity.
Twenty seven one star reviews of the Tenavolts on Amazon:
https://www.amazon.com/product-reviews/B07MCGH26Q/ref=acr_dp_hist_1?ie=UTF8&filterByStar=one_star&reviewerType=all_reviews#reviews-filter-bar
@wjcroft Hi. Here's a link of a video about how potentially dangerous LiPo batteries are:-
It raises again the related issue of having a high capacity Lithium ion battery close to patients in a hospital ward while their EEG data are being streamed and stored by a micro SD card that would be working hard with continual bursts of 200mA, thus posing as a heavy current draw/load on 6600 mAh Lithium ion batteries over a period of 9 to 12 hours with only two or three breaks to allow for changes in the rechargeable 6600 mAh Lithium ion batteries.
The picture of a headband kit displayed in a OpenBCI tutorial with the Cyton board apparently laden with batteries and dangling on the subject's chest is hardly conducive to the safety standards expected in a hospital ward:-
https://docs.openbci.com/docs/04AddOns/01-Headwear/HeadBand
Hence the apparent need for the 6600 mAh Lithium ion battery pack to be placed well away from the patient with the help of the Adafruit battery connection extension leads in this link:-
https://www.adafruit.com/product/1131.
However, apart from risk outlined above, the question that remains to be asked is: Would such an Adafruit battery connection extension lead introduce noise into the EEG data being streamed and recorded?
Where are you getting the 9 to 12 hour figure for a 6600 mAh LiPo? Previously I mentioned:
"As a reality check, the Cyton itself is about 50ma drain. 6600 mAh / 50 mA = about 132 hours / 24 = 5.5 days of power. Adding the Daisy will use more mA, but not twice."
The short higher currrent bursts as blocks are written to the SDcard, likely are of short duration and happen infrequently. I don't think they are going to significantly impact your battery life. You can likely get away with a smaller LiPo, 2200 or 2500 might be plenty, https://www.adafruit.com/category/138 . The 2500 could easily be taped to the back of your board. But you can use any size battery and run the extension power cable, no problem.
Please relax about the risks from the Adafruit batteries. These batteries are safe as long as they are not physically abused by crushing or puncturing.
On the other hand, do be aware of the OpenBCI disclaimer statement, at the bottom of the page,
https://shop.openbci.com/collections/frontpage/products/cyton-biosensing-board-8-channel?variant=38958638542
Some environments may require that all equipment meet CE medical standards. Which OpenBCI explicitly does not do.
https://www.google.com/search?q=ce+medical+standards
Regards, William
All the Adafruit cells include internal protection circuits that limit overcharging, overcurrent, etc. The chargers they sell, similarly.
@wjcroft Thanks for the clarification. For the avoidance of doubt, it seems clear from your answer to my enquiry that the JST-PH Battery Extension Cable - 500mm can be added without the risk of distorting EEG streaming and recording; and, that the Adafruit 3.7 volt 6600 mAh battery would easily outlast/survive a marathon 9 to 12 hour period of continuous streaming and recording of EEG data with the Cyton +Daisy board and 400GB micro SD card even though it is emphatically stated in the description of the 6600 mAh battery that it does not tolerate a sustained load of more than 1.3 amps or 0.2C (unsure about meaning of C here).
So, in conclusion, would I be rest assured that the current draw/load in the above scenario would be less than 1.3 amps over the 9 to 12 hour period that I would be requiring the Adafruit 6600 mAh battery?
The Cyton will never put a load of 1300 milliamps (1.3 amps) on the battery. The extension cable is fine. As I said previously 6600 mAh is likely way over the capacity you need. The 2500 mAh should be fine and eliminates the need to run the extension cord; it can tape on to the back of your Cyton.
@wjcroft. Thanks once more. However, I would prefer to be over-powered with the 6600mAh battery considering that the Cyton Daisy board would have to communicate for 9 to 12 hours by Bluetooth, on a single charge of the battery, with a dongle at the end of a 20-metre superflat USB lead connected to my netbook computer. Thus, I would be sure not to get in the way of nurses attending to the patient by conducting battery level checks during the 12-hour stint. Best regards
Using the JST-PH 2 pin extension cable from Adafruit, or other related connectors, you could place a DVM digital voltmeter / amp meter in series with your battery to measure EXACTLY the current consumption during normal operation. You should get a figure well under 100 milliamps. 50 is the figure for the Cyton alone. The Daisy might add say 20 milliamps. Your SD card usage is going to cause very short barely observable increase in milliamps during buffer writes. These writes are not continuous but only when the buffer fills.
@wjcroft Hi again! Your reality check above for the 6600 mAh Adafruit battery indicated a battery life of 5.5 days, at least in theory.
I am currently using a Nokia 2.1 mobile phone with a 4000 mAh battery. After fully charging the battery, I can browse continuously for about 4 or 5 hours in the course of a day such that well before the end of the day, the lithium ion battery would need recharging. Would not a similar scenario arise with the Cyton Daisy board? As I said before, the purpose of a 6600 mAh Lithium ion battery is to avoid constant checks on battery level so as not to get in the way of nurses and doctors attending to a patient whose EEG I was streaming and recording for private research purposes.
For another reason, using a 6600 mAh Adafruit power pack is more reassuring because some batteries are deliberately overrated. For example, if one were to measure, with a voltmeter, the voltage of the 9 volt EBL rechargeable lithium ion batteries which I am using with a Mind Machine, one may discover to one's surprise that the output voltage when fully charged is actually 7.5 volts.
How realistic, therefore, is the reality check against the background of the Nokia phone illustration given above and taking into consideration that the Adafruit 6600 mAh power pack may possibly be overrated? Is it not conceivable that a Cyton Daisy board with a micro SD card utilises as much current as a phone being used on the internet?
I have read a little about digital multimeters (https://www.toolnerds.com/multimeter/) for the purpose of connecting it in series, as you suggested above, with the 6600 mAh Lithium ion battery and verifying actual 'consumption during normal operation' of the Cyton Daisy board. However, as with all circuits, caution would be required. Having a child around accidentally connect the DVM digital voltmeter/amp meter (especially one without Auto Ranging or overload protection) in parallel or reverse polarity with the 6600 mAh battery pack may be potentially hazardous (https://www.toolnerds.com/multimeter-safety-tips/).
You mention: "I can browse continuously for about 4 or 5 hours in the course of a day such that well before the end of the day, the lithium ion battery would need recharging." Generally phone browsers or phone video players are among the highest power consumption apps. This is because they are making constant use of both the phone CPU, and the phone radio chip for internet data usage.
When new, the phone battery indeed had the rated capacity. But this drops over time, such that after a year of daily use and recharging, the phone battery will have significantly less capacity than when new.
The Adafruit battery ratings are not 'overrated'. The current consumption of the Cyton is quite modest.
The tester here can show battery level when the button is pressed.
https://www.banggood.com/Voltage-Capacity-Display-5-LED-Battery-Indicator-Board-to-1S-2S-3S-4S-3_6V-16_4V-Li-ion-LiPo-Battery-p-1387404.html
With a single LiPo cell, that means ordering the 1S version.
@wjcroft. Thanks for your dedication.
@wjcroft In relation to the above discussion, you may be interested in this battery tester with an adjustable low voltage alarm:
https://www.amazon.com/LiPo-Battery-Checker-Monitor-Indicator/dp/B07BQWSXC4